1. Is it possible to inject new code into a subroutine that will execute within the lexical scope of the subroutine body? That is, can I take 
    sub {
    BLAH
}

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    and convert it (programmatically, not by grovelling around in the original definition) into 
    sub  {
    BLAH
    YOUR CODE HERE
}

    [download]
    Specifically, what I have in mind is taking a subroutine that modifies @_—possibly without modifying its original arguments (say, by splicing entries into the middle)—and applying a user-specified function to the resulting mutated array. (A natural thought is some wrapper like 
    sub inject {
    my ( $outer, $inner ) = @_;
    return sub {
        $inner->(@_);
        goto &$outer;
    }
}

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    but that doesn't work, since $outer is executing in a different lexical scope.)

    I know that B::Deparse will handle the simple case of functions that don't close over external variables, and Data::Dump::Streamer will handle more cases, but I'm looking for something really robust.

  2. Is there a subroutine uneval such that eval uneval($a) always returns $a? Even if it's possible to do this just when $a is a simple scalar (i.e., not a reference), then I'm happy—but I'd like to preserve any ‘magic’ associated to $a (for example, not lose its numeric value by just stringifying). If one could control the lexical scope in which eval'd strings executed, then this would be easy: 
    sub uneval {
    my ( $a ) = @_;
    return ( in_current_scope => '$a' );
}

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    but I'm not sure how to do it otherwise.

UPDATE: I forgot to mention that I wanted to do the unevaling with lexicals, not globals. It's easy with globals: 

our @cache;
my $id = 0;
sub uneval {
    $cache[$id++] = $_[0];
    return __PACKAGE__ . '::$cache[' . $id . ']';
}

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In reply to Modifying subroutines and un-eval-ing by JadeNB

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